The above problems and the state of the art as regards means for handling bed material in plants with a combustor with a fluidized bed are described in detail in a report, ANL/CEN/FE-81-3 from Argonne National Laboratory, Argonne, Il., entitled "Discharge and Handling of Solids from Pressurized Fluidized Bed Combustors" by John E Hanway Jr. and W. F. Podolski.
From DE-C-948 105 a combustion plant with a fluidized bed is known, in which the bed material is constantly discharged from and returned to the fluidized bed. The discharged bed material from the fluidized bed is brought, in a conduit, into contact with a relatively cold compressed gas, which absorbs heat from the bed material In a cyclone the bed material is separated from the gas. The bed material is returned to the fluidized bed, whereas the gas is mixed with the combustion gases from the fluidized bed and supplied to a gas turbine. In this way, the temperature of the gases flowing into the turbine is controlled. The method is not utilized for power control in the combustion plant with the fluidized bed, and the quantity of bed material present in the fluidized bed is constant practically all the time.
In European patent application 84104821.8, publication number 0 124 842, a further power plant of the kind in question is described.